Re: BOOTP/DHCP packets minimum size

[Dan Williams <dcbw redhat com>]

On Sat, 12 Feb 2005, Bill Moss wrote:
> *http://www.clavister.com/releasenotes/changes-8.00.02-to-8.00.05.html
> 
> DHCP relayer would (correctly) refuse too short DHCP packets*
> *Issue:* According to the BOOTP and DHCP RFCs, all BOOTP/DHCP packets 
> must be at least 300 bytes in size, and use padding to reach this size 
> if the actual data is shorter. The DHCP relayer used to verify this size 
> and drop packets
> *Problem:* Some DHCP clients/servers (notably, the Windows 2000 DHCP 
> server) violate the RFCs and send packets shorter than 300 bytes.
> *Results:* Misbehaving clients would be unable to aquire DHCP leases 
> through the DHCP relayer. Misbehaving servers would be unable to hand 
> out DHCP leases through the DHCP relayer.
> 
> This means that the buildmsg.c patch should have the value of PAD_STOP 
> set to a minimum value of 300. This parameter is controlling the size of 
> the DHCP/BOOTP packet. Otherwise, there is a danger that firewalls, and 
> routers configured as DHCP relay agents, may drop the dhcp messages as 
> invalid. Some DHCP servers may refuse to respong to a discover or 
> request that violates this rule.

Bill,

Thanks for that reference.  I will commit the patch I sent you, with the 
PAD_STOP adjusted to be 300.

Dan